Meetings and Events

Southern Ocean Gas Exchange Experiment (GasEx) Meeting
Hilton Washington D.C./Silver Spring
12 September 2007

Description

GCC research is integrated across four over-riding themes:

Global Location, Magnitude and Dynamics of Carbon Sources and Sinks

A variety of atmospheric, oceanic and terrestrial data has shown that both the ocean and terrestrial biosphere currently take up and store a significant portion of the carbon released to the atmosphere as a result of human activities. Preliminary progress has been made on locating sources and sinks of carbon on a regional basis and characterizing their magnitude and behavior over time. The results obtained thus far are at the limit of detection, however, and cannot be extended to many regions of the world due to lack of data. Optimization studies have suggested a few key terrestrial regions in which to locate additional sampling stations. In addition, large areas of the oceans are currently vastly undersampled for the purposes of quantifying regional oceanic source and sink magnitude and variability. Improvements in sampling technology, spatial coverage, process parameterizations and transport models will greatly improve our characterization of global carbon sources and sinks by region.

Northern Hemisphere Carbon Sinks

Atmospheric and oceanic data and models have predicted that the terrestrial sink is larger in the Northern Hemisphere than in the Southern Hemisphere. Recent studies have suggested that a large portion of this terrestrial sink may be located in North America for the period 1988-1992, although there is considerable debate concerning the magnitude and mechanism for this sink. The initial focus of this research theme is to constrain estimates of the Northern Hemisphere terrestrial sink and identify responsible mechanisms using a combination of field experiments, observations, and models.

Causes of Variability in Sources and Sinks

The rate of increase of carbon dioxide in the atmosphere can vary significantly on interannual and decadal time-scales. The causes of this variability are unknown: while a small amount is a result of variations in emissions, the majority is due to variability in uptake by the oceans and terrestrial biosphere. Several factors have been hypothesized to control this variability, including climate modes such as El Nino-Southern Oscillation, historical and current land use, and CO₂ and N fertilization. Studies are needed which investigate how various factors influence global carbon cycle variability over a variety of temporal scales, and identify which factors are the most important.

Future Atmospheric Carbon Dioxide Concentrations

Current models used to project future atmospheric carbon dioxide concentrations assume that the carbon cycle will continue to operate in the same way it has operated in the recent past. These models do not take into account the limitations of the carbon sink on land, or how biological, chemical and physical processes in the ocean and land might change either due to natural variability or external forcing. For example, it has been suggested that long-term uptake and storage of carbon by the ocean may be reduced by climate change, resulting in an increased proportion of carbon dioxide remaining the atmosphere. By examining the carbon cycle as an integrated system, identifying how it interacts with climate and other influences such as land use patterns, and incorporating the carbon cycle into dynamic earth system models, more realistic predictions of future atmospheric carbon dioxide concentrations and potential abrupt changes in growth rate can be made.